Optical head and method of making the same

Abstract

An optical head includes a lens holder for carrying a biconvex lens and a plano-convex lens above a data storage disk. In data-writing or data-reading operation, the plano-convex lens comes closer to the storage disk than the biconvex lens. The plano-convex lens is accommodated in a through-hole formed in the lens holder. The lower opening of the through-hole is closed by a transparent plate attached to the bottom surface of the lens holder. The flat lens surface of the plano-convex lens is held in close contact with the transparent plate.

What is claimed is:  
     
       1. An optical head comprising: 
       a lens holder that is formed with a through-hole and includes an obverse surface and a reverse surface, the obverse surface facing an optical data storage medium;  
       a first lens supported by the lens holder;  
       a second lens arranged in the through-hole, the second lens being closer to the storage medium than the first lens is;  
       a coil that generates a magnetic field; and  
       a transparent plate bonded to the lens holder;  
       wherein the transparent plate includes a first surface on which the coil is provided and a second surface opposite to the first surface, the second lens being bonded to the second surface of the transparent plate.  
     
     
       2. The optical head according to  claim 1 , wherein the transparent plate entirely covers the obverse surface of the lens holder. 
     
     
       3. The optical head according to  claim 1 , wherein the second lens includes a flat lens surface and a non-flat lens surface, the flat lens surface being held in surface contact with the transparent plate. 
     
     
       4. The optical head according to  claim 1 , wherein the second lens is provided with a flange held in engagement with the through-hole of the lens holder. 
     
     
       5. The optical head according to  claim 1 , wherein the first lens is attached to the reverse surface of the lens holder. 
     
     
       6. The optical head according to  claim 1 , wherein the lens holder is made of an electrically non-conductive material. 
     
     
       7. The optical head according to  claim 1 , wherein the second lens and the transparent plate are equal in refractivity. 
     
     
       8. The optical head according to  claim 1 , wherein each of the first and the second lenses is an achromatic lens. 
     
     
       9. The optical head according to  claim 1 , wherein the second lens and the transparent plate are complementary to each other in thickness. 
     
     
       10. The optical head according to  claim 1 , wherein the lens holder is supported by an elastic suspension so as to float above the storage medium when the storage medium rotates. 
     
     
       11. An optical disk apparatus comprising: 
       a data-recording optical disk including a first surface and a second surface opposite to the first surface;  
       a first optical head facing the first surface; and  
       a second optical head facing the second surface and arranged symmetrically to the first optical head with respect to the optical disk;  
       wherein each of the first and the second optical heads comprises:  
       a lens holder formed with a through-hole;  
       a plano-convex lens arranged in the through-hole and including a flat lens surface; and  
       a transparent plate bonded to the lens holder and held in surface contact with the flat lens surface of the plano-convex lens.  
     
     
       12. The optical disk apparatus according to  claim 11 , wherein the first and the second optical heads are urged toward the optical disk with a substantially equal force. 
     
     
       13. A method of making an optical head comprising the steps of: 
       preparing a transparent first plate;  
       forming a plurality of coils on the first plate;  
       forming an insulating protection layer that covers the coils;  
       preparing a second plate formed with a plurality of through-holes;  
       producing a plate assembly by bonding the first and the second plates to each other; and  
       placing a lens in each of the through-holes;  
       wherein the lens is bonded to the first plate in the lens placing step.  
     
     
       14. The method according to  claim 13 , further comprising the step of cutting the plate assembly in a manner such that each of the through-holes is kept undivided. 
     
     
       15. The method according to  claim 13 , further comprising the step of reducing a thickness of the first plate after the protection layer forming step and before the plate assembly producing step.